Commit 1966554b authored by Nilay Shroff's avatar Nilay Shroff Committed by Jens Axboe
Browse files

block: fix module reference leak in mq-deadline I/O scheduler 



During probe, when the block layer registers a request queue, it
defaults to the mq-deadline I/O scheduler if the device is single-queue
and the mq-deadline module is available. To determine availability, the
elevator_set_default() invokes elevator_find_get(), which increments the
module's reference count. However, this reference is never released,
resulting in a module reference leak that prevents the mq-deadline module
from being unloaded.

This patch fixes the issue by ensuring the acquired module reference is
properly released.

Fixes: 1e44bedb ("block: unifying elevator change")
Signed-off-by: default avatarNilay Shroff <nilay@linux.ibm.com>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250719132722.769536-1-nilay@linux.ibm.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 2680efde

block/elevator.c

+13 −6
Original line number Diff line number Diff line
@@ -719,7 +719,8 @@ void elevator_set_default(struct request_queue *q) 
		.name = "mq-deadline",

		.no_uevent = true,

	};

	int err = 0;

	int err;

	struct elevator_type *e;



	/* now we allow to switch elevator */

	blk_queue_flag_clear(QUEUE_FLAG_NO_ELV_SWITCH, q);
@@ -732,12 +733,18 @@ void elevator_set_default(struct request_queue *q) 
	 * have multiple queues or mq-deadline is not available, default

	 * to "none".

	 */

	if (elevator_find_get(ctx.name) && (q->nr_hw_queues == 1 ||

			 blk_mq_is_shared_tags(q->tag_set->flags)))

	e = elevator_find_get(ctx.name);

	if (!e)

		return;



	if ((q->nr_hw_queues == 1 ||

			blk_mq_is_shared_tags(q->tag_set->flags))) {

		err = elevator_change(q, &ctx);

		if (err < 0)

		pr_warn("\"%s\" elevator initialization, failed %d, "

			"falling back to \"none\"\n", ctx.name, err);

			pr_warn("\"%s\" elevator initialization, failed %d, falling back to \"none\"\n",

					ctx.name, err);

	}

	elevator_put(e);

}



void elevator_set_none(struct request_queue *q)